ON THE DOCTRINE OF PHLOGISTON. 67 



has got from the finery cinder mull be feparated from it, and to leave oxide of 

 enter into the fame calx again. But while the heat continues cannot happen 

 the fame, I deem thefe contrary effects to be impoflible. If at the fame heat, 

 the degree of heat that is applied expel oxigen from the calx, 

 it will certainly prevent its return. Confequently, if fixed air 

 be formed, it cannot be decompofed in thefe circumftances. 



2. If it was pofhble for oxigen to be feparated from finery Carbon being 

 cinder without any thing entering into it, which I think can -^ r n ,Jjfn rc d n * s one 

 not be done, it could not, according to the new theory, form compound with 

 any thing by its union with carbon befides fixed air ; this be- oxigen (namely 

 ing faid to be carbon diflblved in oxigen gas, but nothing in- concltaded that 

 flammable could be produced by their union. Of this Mr. n p inflammable 

 Cruickfhank is fenfible, and therefore he was under the ne- in r red y Cin g 

 ceffity of fuppofing that, after the oxigen had quitted the finery finery cinder 5 

 cinder, it muft enter into it again. But if this were poffible,™^* mcau * 

 nothing would remain of the fixed air but carbon, as before that 



union ; and this is a folid fubftance, incapable, without the 

 aid of oxigen, of afluming the form of air. Whence, then, 

 comes the inflammable air in this procefs, which fo nearly re- 

 fembles that from charcoal and water, that they muft have 

 the fame origin ; and with refpecl to this, Mr. Lavoifier de- 

 cides, that whatever is inflammable in it muft come from 

 water. 



3. Admitting all that Mr. Cruickfhank alledges concerning The mflarnma- 



the difference in fpecific gravity, and other circumftances, be- ^k S as > t ^ ou 5 h 



1 • r *> • 1 »i , > i 1 • - different from 



tween the air from finery cinder and charcoal, and that from that obtained by 



water and charcoal, it is not fo great as the difference between cnarc oa] and 

 the latter and the light inflammable air from the metals with ox }d e but a corn- 

 acids or water. Different as they may be in other refpecls, buftiblc. 

 they are all inflammable, and have the common property of 

 uniting with oxigen in a certain degree of heat ; in confe- 

 quence of which they are the reverfe of oxides, and muft be 

 clafled with combujiibk fubftances, equally with fulphur and 

 phofphorus. 



4. If the oxigen, after quitting the finery cinder, entered The oxigen doet 



into it again, it would make it finery cinder as at the firft, " ot retu . rn t0 tn * 



1 n • r 1 1 11. 11 finery cinder 5 



or at leaft in iome degree ; whereas the calx is completely re- for the iron is 



vived in this procefs, the iron (o revived being as foluble in ^""d and con- 



., . , . tinues fo. 



acids as any iron whatever. 



5. If the iron fhould be completely revived by the oxigen Iron cannot de- 

 wholly leaving it, I ftill maintain that it could not, by any com P°fe **& 



F2 degree eipwiswntWfr 



